Method for making liquid or semi-liquid fermented milk products

ABSTRACT

A method for making liquid and semi-liquid fermented milk products, including the following steps:
         a) placing a milk-based mixture in a container;   b) subjecting the basic mixture to a heating thermal treatment;   c) adding lactic bacterial strains to the basic mixture according to a concentration of at least 10̂8 CFU/ml of basic mixture, and subjecting the basic mixture to which tic bacterial strains were added to a thermal treatment for a predetermined time;   d) stirring the mixture to which lactic bacterial strains were added in order to break a coagulated mass which formed in the mixture to which lactic bacterial strains were added, to make the liquid and semi-liquid milk products.

BACKGROUND OF THE INVENTION

This invention relates to a method for making liquid or semi-liquidfermented milk products.

This invention applies to the field of machines for the production,storage and dispensing of fermented milk products such as artisan yogurtand similar dairy products which are distributed in commercialestablishments such as ice cream and yogurt parlors, confectioners shopsand the like, designed to sell to consumers natural yogurt produced in acraftsman-like fashion, if necessary with the addition of toppings.

In this context, conventional machines are known for the production offermented milk products such as milk pasteurizing machines, devices forfermenting inoculated milk and refrigerating machines for storingfermented milk products, once produced.

These conventional machines allow the production of fermented milkproducts according to a production cycle defined by a predeterminedsequence of operating steps which are described below.

Initially, an operator introduces the milk used for the production offermented milk products into a containment tank of the pasteurizingmachine. The pasteurizing machine heats the milk contained in the tank.

Once the pasteurizing of the milk has been completed, the milk is cooledin the containment tank of the pasteurizing machine and inoculated withmilk ferments.

Subsequently, the operator draws the cooled and inoculated pasteurizedmilk (from the pasteurizing machine) and places it in a fermentationtank (of a fermenting device).

The fermentation tank reaches a predetermined fermentation temperaturewhich is maintained for a predetermined time, in such a way as to inducethe growth of the bacteria present.

Once the fermentation has been completed, the fermented milk is cooledto a storage temperature, and after this has been reached the productioncycle of the fermented milk is completed.

At this point, the operator introduces the fermented milk produced intosuitable refrigerating machines which keep the product at apredetermined temperature in such a way as to store it over time.

The above-mentioned conventional machines have several drawbacks.

Firstly, the use of a plurality of machines/devices for performing thefermented milk production cycle necessarily requires the presence of aproduction operator, from the pasteurization of the milk up to theobtaining of the fermented milk, thus considerably increasing the costsof the finished product due to the labor costs.

Moreover, the use of several machines/devices for making the fermentedmilk is particularly disadvantageous in terms of space dedicated forinstalling them in a small-scale artisan facility.

A further drawback and one which is even more highly felt is that linkedwith the lengthy time required for making a batch of fermented milk,which does not allow for a particularly high productivity unless thereare a particularly high number of machines available (with added costsand reduced space available in the sales outlets).

SUMMARY OF THE INVENTION

The aim of this invention is to provide a method for the production offermented milk products which overcomes the above-mentioned drawbacks.

Yet another aim of the invention is to provide a method for makingfermented milk products which provides a particularly high productivity.

According to the invention, these aims are achieved by a method forproducing fermented milk products comprising the technical features setout in one or more of the accompanying claims.

BRIEF DESCRIPTION OF THE DRAWINGS

The technical features of the invention, with reference to the aboveaims, are clearly described in the claims below and its advantages areapparent from the detailed description which follows, with reference tothe accompanying drawing which illustrates a non-limiting exampleembodiment of the invention and in which:

FIG. 1 is a side view of a machine which actuates the method for makingfermented milk products according to this invention.

DESCRIPTION OF THE PREFERRED EMBODIMENTS

With reference to the accompanying drawing, the numeral 100 denotes anapparatus, that is, a machine, for implementing the method according tothe invention.

The machine 100 is a crushed-ice drink maker of the pasteurizing type.

The machine 100 is illustrated purely by way of an example, as themethod could also be actuated in machines of a different type.

Irrespective of the machine 100, the method for making a liquid andsemi-liquid product of the fermented milk type (preferably natural orwith toppings) comprises, according to this invention, the followingsteps:

-   -   a) placing a milk-based mixture (known hereinafter also as the        basic mixture) inside a container 3 (preferably a tank);    -   b) subjecting the basic mixture to a heating thermal treatment;    -   c) adding lactic bacterial strains to the basic mixture        according to a concentration of at least 10̂8 CFU (microbial        cells)/ml of basic mixture, and subjecting the basic mixture to        which bacterial strains were added to a predetermined thermal        treatment for a predetermined time;    -   d) stirring the mixture to which lactic bacterial strains were        added in order to break the coagulated mass which formed in the        mixture to which lactic bacterial strains were added, thereby        making the liquid and semi-liquid product of the fermented milk        type.

Preferably, the step c comprises adding to the basic mixture lacticbacterial strains according to a concentration equal to or greater than10̂9 CFU/ml of basic mixture.

Still more preferably, the lactic bacterial strains comprise a mixtureof Lactobacillus bulgaricus and Streptococcus thermophilus ifyogurt-style fermented milk is to be produced.

It should be noted that it has been found by experimentation that aconcentration of lactic bacterial strains greater than 10̂8 CFU/ml ofmilk-based mixture means that the production time of the fermented milkproduct is drastically reduced, whilst at the same time maintaining ahigh quality of the end product.

More specifically, experimental tests have shown times of less than 3hours (that is, less than half that of prior art processes) for makingfermented milk.

Advantageously, this translates into an immediate increase inproductivity, with a consequent reduction in costs for the point of saleoperator.

According to one aspect, the step c) of adding lactic bacteria strainsto the basic mixture r say comprise the following steps:

-   -   extracting a portion of the basic mixture from the container 3;    -   adding the lactic bacterial strains to the portion of basic        mixture extracted:    -   stirring the portion of mixture to which lactic bacterial        strains were added;    -   putting the portion of mixture to which lactic bacterial strains        were added back into the container 3.

It should be noted that, preferably, the container 3 is provided with astirrer 2 and with thermal treatment means (not illustrated), configuredfor thermally treating the mixture inside (preferably by thetransmission of heat through the lateral walls of the container 3 orthrough the lateral walls of a heat exchanger positioned inside thecontainer 3).

Preferably, the container 3 is a tank.

It should be noted that inside the tank 3 there is a cylinder, on thesurface of which there is the stirrer 3.

The cylinder is associated with a heat exchanger of a refrigeratingsystem, the coils of which are positioned inside the cylinder so as toexchange heat through the walls of the cylinder.

According to another aspect, the method comprises a further step ofadding sugar (preferably saccharose).

Preferably, according to this aspect, the method comprises a step ofadding a quantity of sugar.

The quantity of sugar added can be varied by the operator based on theparticular flavors.

Preferably, the percentage of sugar in the mixture is less than 70% (byweight).

More preferably, the percentage of sugar is between 20% and 30% byweight of the milk-based mixture.

It should be noted that, preferably, after the step of adding sugarthere is a step of mixing and cooling the finished product, inside amachine for the production of soft ice cream (not illustrated).

This step is implemented in particular inside the mixing and coolingcylinder of a machine for the production of soft ice cream, which isequipped with a device for stirring and with thermal treatment means.

This additional step makes it possible to stabilize further the productand to increase the quality of the product from the organoleptic pointof view.

With particular reference to the above-mentioned step b) of subjectingthe basic mixture to a heating thermal treatment, the method comprises astep of heating the basic mixture to a temperature value of between 38°C. and 45° C. (even more preferably to a temperature value of between41° C. and 43° C.).

Preferably, the step b) comprises stirring the basic mixture.

Still more preferably, after the step b) there is a step of keeping thebasic mixture stationary, that is, without stirring and thermaltreatment (preferably at the temperature reached in step b), for apredetermined time.

Moreover, the step c) comprises a step E) of keeping the basic mixtureat a temperature value of between 38° C. and 45° C. (even morepreferably at a temperature value of between 41° C. and 43° C.) for apredetermined time.

The step E) of keeping the basic mixture at a temperature value ofbetween 38° C. and 45° C. comprises two sub-steps:

-   -   E1) a first sub-step in which the milk-based mixture to which        lactic bacterial strains were added is subjected to stirring;    -   E2) a second sub-step in which the milk-based mixture to which        lactic bacterial strains were added is kept stationary, that is        to say without stirring.

It should be noted that the first sub-step E1 precedes the secondsub-step E2

Preferably, the first sub-step has a duration of less than 10 minutes(more preferably it is less than 5 minutes).

Preferably, the second sub-step E2 has a duration less than or equal to3 hours.

It should be noted that, for example, but without restricting the scopeof the invention, step E) comprises an intermittent activation of athermal treatment system which allows the set temperature to bemaintained.

Purely by way of an example, the thermal system is activated in thisstep E) for a percentage of time of between 25% and 50%—still morepreferably between 30% and 40%—and turned off for the remaining time.

The coagulated mass which forms naturally in the mixture is broken instep d), to obtain a homogeneous and creamy structure.

It should be noted that the coagulated mass is broken by stirring thebasic mixture to which lactic bacterial strains were added in thecontainer 3.

According to this process, the coagulation of the fermented milk occursin the container 3.

Further, after the step d), the method comprises a step of cooling theproduct to a temperature for storage of the product of between 0° C. and5° C. (preferably equal to 4° C.).

According to this aspect, the method comprises a step of stirring theproduct intermittently (that is, according to on-off cycles) orcontinuously during the cooling: this prevents the formation of iceinside the container during the cooling (which would cause a degradationof the quality of the product).

It should be noted that the method also comprises a step for dispensingthe product from the container 3, for its storage or distribution.

It should be noted that the sequence of steps described above makes itpossible to obtain large quantities of fermented milk in an extremelyshort time the (a few hours), increasing the overall productivity of thesales outlets.

Further, according to another aspect, the fermented milk is subjected toa subsequent step of simultaneous cooling and stirring, that is, ofsubjecting the fermented milk to mixing and cooling.

In this way, the fermented milk is subjected to mixing and cooling, toobtain a finished product (for example ice cream) which has an increasedvolume due to the effect of incorporating air during the simultaneouscooling and stirring.

Preferably, the fermented milk is subjected to mixing and cooling afterhas been added to it

The mixing and cooling step occurs inside a machine for the productionof soft ice cream.

1. A method for making a liquid and semi-liquid product of the fermented milk type, comprising the following steps: a) placing a milk-based mixture in a container; b) subjecting the basic mixture to a heating thermal treatment; c) adding lactic bacterial strains to said basic mixture according to a concentration of at least 10̂8 CFU/ml of basic mixture, and subjecting said basic mixture to which lactic bacterial strains were added to a thermal treatment for a predetermined time; d) stirring said mixture to which lactic bacterial strains were added in order to break a coagulated mass which formed in said mixture to which lactic bacterial strains were added, thereby making said liquid and semi-liquid product of the fermented milk type in the container, said lactic bacterial strains comprise a mixture of Lactobacillus bulgaricus and Streptococcus thermophilus to obtain yogurt-style fermented milk.
 2. The method according to claim 1, wherein said liquid and semi-liquid product of the fermented milk type is yogurt.
 3. The method according to claim 1, wherein said step of adding to said basic mixture lactic bacterial strains according to a concentration of at least 10̂8 CFU/ml of basic mixture comprises adding to said basic mixture lactic bacterial strains according to a concentration greater than 10̂9 CFU/ml of basic mixture.
 4. The method according to claim 1, wherein step c) of adding lactic bacterial strains to said basic mixture comprises the following steps: extracting a portion of said basic mixture from the container; adding the lactic bacterial strains to the portion of basic mixture extracted: stirring the portion of mixture to which lactic bacterial strains were added; putting said portion of mixture to which lactic bacterial strains were added back into the container.
 5. The method according to claim 1, comprising a further step of adding sugar.
 6. The method according to claim 5, wherein a quantity of sugar is added to the basic mixture, as a percentage being less than 70% by weight of the mixture.
 7. The method according to claim 6, wherein the fermented milk is subjected to a subsequent step of cooling simultaneously with stirring, for carrying out stirring and freezing of the fermented milk.
 8. The method according to claim 1, wherein said step b) of subjecting said basic mixture to a heating thermal treatment comprises a step of heating said basic mixture to a temperature value of between 38° C. and 45° C.
 9. The method according to claim 8, comprising, after said step b) of subjecting the basic mixture to a heating thermal treatment, a step of keeping said basic mixture stationary for a predetermined time at a temperature value reached during said step b) of subjecting said basic mixture to a heating thermal treatment.
 10. The method according to claim 9, wherein said predetermined time is a time of between 5 and 15 minutes.
 11. The method according to claim 1, wherein said step c) of adding lactic bacterial strains to said basic mixture and subjecting said basic mixture to which lactic bacterial strains were added to thermal treatment comprises a step e) of keeping said basic mixture at a temperature value of between 38° C. and 45° C. for a predetermined time.
 12. The method according to claim 11, wherein said step e) of keeping said basic mixture at a temperature value of between 38° C. and 45° C. comprises the following sub-steps in the following time order: e1) a first sub-step in which the milk-based mixture to which lactic bacterial strains were added is subjected to stirring; e2) a second sub-step in which the milk-based mixture to which lactic bacterial strains were added is kept stationary, that is to say without stirring.
 13. The method according to claim 12, wherein the first sub-step e1), in which the milk-based mixture to which lactic bacterial strains were added is subjected to stirring lasts for less than 10 minutes.
 14. The method according to claim 12, wherein the second sub-step e2, in which the milk-based mixture to which lactic bacterial strains were added is kept stationary, that is to say, without stirring, comprises intermittent activation of a thermal treatment system. 